1. Field of the Invention
The invention relates to accessing of subscriber identity cards, and more particularly to accessing subscriber identity cards using dedicated controllers.
2. Description of the Related Art
Currently, the Global System for Mobile communication (GSM) standard is a popular standard for mobile phones in the world. The GSM standard, standardized by the European Telecommunication Standards Institute (ETSI) is a cellular network structure and a Time Division Multiple Access (TDMA) system. For a carrier frequency, the TDMA system will divide a frame into eight time slots, wherein each time slot is used to transmit a channel data for a subscriber. Meanwhile, General Packet Radio Service (GPRS) technology is one of the available technologies provided by GSM systems. The GPRS technology utilizes the unused channels in the GSM system to provide moderate speed data transmission. The Wideband Code Division Multiple Access (W-CDMA), is a wideband spread-spectrum mobile air interface that utilizes a direct-sequence spread spectrum method for asynchronous code division multiple access to achieve higher speeds and support more users compared to the implementation of time division multiplexing (TDMA) used by GSM systems. Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) is another type of 3G mobile telecommunications standard.
A dual SIM mobile phone is a phone with two Subscriber Identity Modules (SIMs), which correspond to different telephone numbers. The dual SIM mobile phone allows a user to use two communications services without carrying two phones at the same time. For example, the same mobile phone may be used for business and private use with separate numbers and bills, thus providing convenience to mobile phone users. In the typical architecture, the dual SIMs are connected to an analog switching device, such that a single controller can access the designated SIM by controlling the analog switching device. To access one SIM, however, the controller has to wait for completion of the other if necessary. The sequential arrangement for accessing SIMs consumes more battery power and is required to be reduced.